Recent data indicate that 2-nitropropane, a widely used chemical precursor and solvent in paints and varnishes, is a potent hepatocarcinogen in rats. The mechanism of carcinogenicity of this nitroalkane, which appears to represent a new class of chemical carcinogen, is unknown. The hypothesis is presented that azoxyisopropane is formed during the reductive metabolism of 2-nitropropane and that it is the azoxy compound which represents that actual carcinogen. To test this hypothesis, 14C labeled 2-nitropropane and 1-nitropropane (which is believed to be non-carcinogenic) will be synthesized and metabolism studies will be done in vivo with Sprague Dawley rats and, under anaerobic conditions, with intestinal microflora and liver fractions, to determine whether the corresponding azoxy compounds are indeed formed. While structural considerations make it likely that azoxyisopropane and azoxypropane, like azoxymethan,e azoxyethane and other aliphatic azoxy compounds, should be strongly carcinogenic, the azoxypropanes have not yet been assayed in animals. Thus as a corollary to the above hypothesis, both azoxyisopropane and azoxypropane will be synthesized and tested for carcinogenicity in male Sprague Dawley rats. Because of the industrial importance of various nitroalkanes as fuels, solvents and precursors, these studies will yield information which will be important in assessing the risk of human exposure to this class of chemicals.